Possible mechanisms of control of gene expression for the onco-developmental serum protein alpha-fetoprotein (AFP) will be explored. Quantitation of the number of AFP genes in rat liver, kidney and Hepatoma 7777 indicate that AFP is transcribed from non-repetitive DNA and the number of AFP genes is approximately 2.0 for each of these tissues. Enhanced levels of AFP synthesis are observed in fetal and neonatal liver up to six weeks of age, after hepatocarcinogen exposure, following exposure to chemicals such as phenobarbitol, during restitutive proliferation after partial hepatectomy or chemically induced necrosis, and in hepatocellular and endodermal sinus (Yolk Sac) tumors. Data on neonatal liver and four selected transplantable hepatocellular carcinomas indicate that changes in AFP synthesis correlate with the cellular accumulation of AFP mRNA. These results suggest that the level of expression of AFP in these tissues is mainly regulated by modulating the steady state concentration of the corresponding functional mRNA. The question as to how the steady-state level of AFP mRNA is modulated during liver development and oncogenesis remains to be answered. Although specific gene amplification cannot be ruled out completely, further investigation will concentrate on regulatory mechanisms involving transcriptional control or modulation at the level of RNA processing and/or transport into the cytoplasm. We intend to focus our attention therefore on the following: 1) Structure, organization and sequence of the AFP gene and possible relationships to transcriptional control. 3) Relative abundance, and complexity and stability of AFP messenger sequences in the nucleus and cytoplasm at steady state. 3) Identification of primary nuclear precursors, stability of nuclear AFP primary messenger transcripts, and pathways of processing to active mRNA. These studies should not only provide significant insights into the relationship of AFP production to carcinogenesis but also provide basic information on gene control mechanisms of eukaryotic cells.